How much home AC voltage variance is too much?

Not at all. That range is normal.

Anything within a 5% variance is normal - 114 - 126 volts. FWIW, my power here usually stays within a +- 2 volt variance, 118 - 122 volts. I am just outside of Washington, DC. The power company is PEPCO, Potomac Electric Power Company.

-RW-

Agree with with Rlwainwright.The units that add/subtract voltage, do terrible things to the sound.Great for TVs and computers,if needed.

I have seen way more variance then that over the years. The BPT units get great reviews.

Banpuku,
There is some advantage to keeping the input voltage on tube equipment at or slightly below 120v, as the voltage on the tubes and to some extent their lifetime is proportional to it.

If you use an isolation transformer, many of these have selectable taps on the input side with allow you increase or decrease the output voltage by a few volts. The voltage here at lakeside is consistently 122-124, so I dropped the voltage by 4 volts to account for it.

If you don't use a voltage adjustable transformer, I wouldn't worry, as yours are small variations and they won't cause any harm.

Banpuku,
I agree with Zargon......

I have been measuring my AC voltage of my dedicated circuits for my audio system. During the past 24 hours, the voltage has ranged from 121.5 to 122.3 volts.

Loaded? Or without a connected load?
The correct way to measure the voltage at the receptacle is with a load connected to the circuit. Not just at idle but with music playing at a level you normally listen.
The more dynamic the music material the better for a true measurement.

Mine fluctuates between 116 > 108!!!!

I would say you are pretty lucky!
Your household voltage iss stable and not really high.
Enjoy the music!

The National Grid my electric company states within +/- 10% of 208/230Vac residendial and 480Vac commercial. Not responcable for 120 as it is part of 208/230Vac. Brown outs and spikes have to do with condition and load of the system as a whole and have no control over.

Old house poorly wired and I'm the last house on this line!!!

Two Exact Power EP15A's, one for each channel (amp), has solved the problem for now.